Method of manufacturing smooth-surface sheet materials

ABSTRACT

Smooth-surface sheet materials are produced by forming a napless, nonwoven fibrous sheet by applying to the nap on the surface of a needle punched nonwoven fibrous sheet consisting essentially of synthetic fiber either a solvent or swelling agent for at least a part of the material constituting the nap, and subjecting the sheet to pressing, thereby laying and bonding the nap over the surface of the sheet, and impregnating the fibrous sheet with a polyurethane elastomer and covering the surface of the fibrous sheet with a layer of polyurethane elastomer.

United States Patent Nagoshi et al.

[ Feb. 29,1972

[54] METHOD OF MANUFACTURING SMOOTH-SURFACE SHEET MATERIALS [72] Inventors: Kazuo Nagoshi; l-liroshi Hayanami, both of Kurashiki Japan [73] Assignee: Kuraray Co. Ltd., Kurashiki, Japan [22] Filed: Sept. 29, 1969 I [21] Appl.No.: 862,088

Related US. Application Data [63] Continuation-in-part of Ser. No. 563,999, July 11,

1966, abandoned.

[52] US. Cl ..8/130.l, 8/DIG. 4, 8/D1G. 11, 117/161 KP, 117/140 A, 161/64, 161/67 [51 1 Int. Cl. ..D06m [58] Field of Search ..8/130.1, DIG. 4, DIG. 11;

161/64, 67; 117/140 A, 161 KP [56] References Cited UNITED STATES PATENTS 2,841,205 7/1958 Bird 161/67 3,014,830 12/1961 Stallard et al ...8/D1G. 4 3,236,586 2/1966 Humphreys ..8/l30.l

Primary ExaminerDonald Levy Assistant Examiner-John C. Cooper, 111 Attorney-Stevens, Davis, Miller & Mosher [57] ABSTRACT elastomer.

1 Claims, No Drawings METHOD OF MANUFACTURING SMOOTH-SURFACE SHEET MATERIALS This application is a continuation-in-part of our copending application Ser. No. 563,999, filed July ll, 1966 now abandoned.

This invention relates to a method of manufacturing smooth surface sheet materials.

Nonwoven fibrous sheet, the fibers of which are bonded to one another by applying an adhesive, needling, shrinkage, or other treatment on the fiber mass, have been widely used as substitutes for woven fabrics including particularly paddings, filters, medical and sanitary supplies, tapes, and ribbons. More recently, a process has been developed wherein a nonwoven fibrous sheet or nonwoven fibrous sheet impregnated with a suitable polymer solution is used as a substrata, on the surface of which a flexible polymer solution is coated and the polymer solution is foamed or wet-coagulated to form sheet material having sponge structure, thereby producing a substitute for leather.

In the manufacture of such sheet materials, leatherlike sheet materials having smoothsurfaces cannot be obtained without difficulties if the substrata are nappy and unsmooth on the surface.

Nonwoven fibrous sheets for use as substrata for artificial leathers are usually subjected to needle punching. The operation tendsto leave needle marks behind and make the substrata all the more nappy because the needles drive part of the fibers out ofthe opposite side of the substrata.

In order to eliminate the surface irregularity and nap, it may be suggested to slice off the surface with a slicer or abrade the surface with sandpaper. However, these treatments cannot completely remove the nap but may rather produce additional nap.

Another possible treatment is singeing of the nap. However, this again involves difficulties in industrial operation. Especially, singeing of nonwoven fibrous sheets of synthetic fibers for the removal of fine nap from the surface often causes fusing of the nap into small balls on the surface instead of removing the nap as is the case with natural fibers.

It is therefore an object of the invention to provide a method of manufacturing leatherlike sheet materials which are smooth on the surface.

The method of the invention comprises forming a napless, nonwoven fibrous sheet by applying to the nap on the surface of a needle punched nonwoven fibrous sheet either a solvent or swelling agent for at least a part of the material constituting the nap, and subjecting the sheet to pressing or hot pressing, thereby laying and bonding the nap flat over the surface of the sheet, impregnating the fibrous sheet with a polyurethane elastomer and covering the surface of the fibrous sheet with a layer of polyurethane elastomer.

The fibrous sheet may be impregnated and covered with a polyurethane elastomer (l) by impregnating the fibrous sheet with a solution of a polyurethane elastomer, spraying or coating the fibrous sheet with the same or different solution of polyurethane elastomer and then wetor dry-coagulating both solutions or (2) by impregnating the fibrous sheet with a solution of polyurethane elastomer, coagulating the impregnated solution, coating or spraying the impregnated fibrous sheet with a solution of polyurethane elastomer and then wetor drycoagulating the coated solution.

According to the method of the invention, leatherlike sheet materials having smooth-surfaces can be easily manufactured.

For the treatment of nonwoven fibrous sheet with a solvent or swelling agent, various methods customarily used for the As solvents or swelling agents, there may be used calcium chloride in methanol, zinc chloride in methanol, aqueous solution of zinc chloride, aqueous solution of phenol, tetrahydrofuran and dimethylformamide.

The present invention will be described in more detail in conjunction with examples thereof, in which, unless otherwise specified, all parts are by weight.

EXAMPLE 1 Staple fibers of nylon-6 of 3-denier and 60 mm. in length, were formed into a random web, and four webs were laminated, and then the resulting laminate was needle punched to form three dimensional unwoven fabric of 400 g./m. The unwoven fabric thus produced was sprayed evenly with a solution of 5 parts of calcium chloride dihydrate in parts of methanol in such a rate that 10 to 20 g. of the solution was deposited on each square meter of the fabric. After the spraying, it was observed that the calcium chloride in methanol spraying solution stuck on the naps of the fabric in the form of fine droplets. Prior to evaporation of methanol after the spraying, the unwoven fabric was passed through a hot press controlled at 1 10 C., and the naps were swelled by the solution of calcium chloride in methanol and bonded to the substratum resulting in no trace of naps on the fabric. On the resulting unwoven fabric, a solution of polyurethane elastomer in admixture with various additives in dimethyl formamide was applied and the polyurethane elastomer was impregnated between the fibers. Further, in order to form a grain surface on the surface, the fabric surface was coated with a solution of polyurethane elastomer mixed with pigment and other ingredients in dimethyl formamide and the coated film was coagulated. Thereafter, the fabric was washed with warm water to remove the solvent of dimethyl formamide and residual calcium chloride, and then dried. A leatherlike sheet material thus obtained had a fine surface. On embossing and lacquering, it was sufficiently adapted for such applications as shoes, briefcases, and suitcases.

EXAMPLE 2 The same treatment as described in Example 1 was carried out, except that a needle punched unwoven fabric of 200 g./m. was used which was formed of mix-spun fibers of 2-denier and 65 mm. in length, produced by spinning a mixture of 40 parts of nylon-6 and 60 parts of polystyrene. That is, the unwoven fabric was sprayed with a solution of calcium chloride in methanol and pressed to bond naps to substratum. The unwoven fabric was impregnated and coated with a solution of polyurethane elastomer in dimethyl formamide and the impregnated and coated solution was coagulated. The impregnated and coated fabric was washed and dried to obtain a sheet material. The material was further treated in toluene at 70 C. to extract and remove polystyrene from the mix-spun fibers. The sheet thus obtained was flexible and had a fine surface. Upon embossing and lacquering, it had a leatherlike appearance particularly suitable for making coats, jumpers, and suits.

EXAMPLE 3 v The same fibers as described in Example 2 were used to form needle punched unwoven fabric of 350 g./m. The fabric was sized with an aqueous solution of polyvinyl alcohol and pressed to compress and set the fabric to a specific gravity of 0.28. The needle marks due to punching left on the fabric surface were not eliminated by the compressing and setting, so that the fabric was passed along a sandpaper roll and the surface was partially ground away in order to attain an increased smoothness.

Although the papering improved the smoothness of surface, it also formed numerous fine naps. Therefore, the naps were eliminated by a solution of calcium chloride in methanol in the same way as in Example 1. This unwoven fabric was impregnated and coated with polyurethane elastomer and Inn/\n: Inna polystyrene was extracted as described in Example 2 to obtain a flexible leatherlike sheet material which had a smooth surface free from any fine protrusions of naps. It was most suitable for shoe uppers.

EXAMPLE 4 Unwoven fabric of 350 g./m. was formed of polyethylene terephthalate fibers having 3-denier and a length of 40 mm. The fabric was needle punched alternately from the both sides, so that it has naps. Therefore, the fabric was not used directly. By means of rollers the fabric was coated with a 70 percent aqueous solution of phenol at such a rate that phenol was applied in the amount of 20 g./m. on the fabric surface. The fabric was then hot pressed twice to obtain very smooth surface. After the phenol was washed away with water, the unwoven fabric was dried. Polyurethane elastomer was deposited between the fibers and wasalso coated on the surface of the fabric to obtain a smooth and resilient leatherlike sheet material.

EXAMPLE 5 A needle punched unwoven fabric consisting of polyacrylonitrile fibers of 2.5-denier was impregnated with polyurethane elastomer and the polyurethane elastomer was coagulated to produce a 0.8 mm.thick porous sheetlike material. The material thus obtained was sprayed with a dimethyl formamide in an amount of g./m. of the sheet.

Immediately after the spraying, the fabric was passed by press roller heated at C. to bond naps to the fabric. Thereafter, 14 percent solution in dimethyl formamide of polyurethane elastomer, which was a reaction product of polyethylene propylene adipate, diphenylmethane diisocyanate and butanediol, was coated thinly on the fabric by means of a roll coater in such a rate that the amount of the resin coated was 5.0 g./m. The coated resin was coagulated in water containing dimethyl formamide in a concentration of 30 percent at 35 C. After removal of the solvent and drying, a leatherlike sheet material was obtained which had smooth and uniform coat. The leatherlike product, when colored by spraying, was suitable to use for clothes.

What we claim is:

l. A method of manufacturing smooth-surface sheet material which comprises forming a napless, nonwoven fibrous sheet by applying to the nap on the surface of a needle punched nonwoven fibrous sheet consisting essentially of synthetic fiber a material selected from the group consisting of a solvent and a swelling agent for at least a part of the material constituting the nap, and subjecting the sheet to pressing, thereby laying and bonding the nap over said surface of the sheet, and impregnating the fibrous sheet with a polyurethane elastomer and covering said surface of the fibrous sheet with a solution of polyurethane elastomer and then wet -or drycoagulating the coated solution. 

